The surgical reconstruction of the bony skeleton is a common procedure in current medical practice. Regardless of the anatomical region or the specifics of the reconstructive procedure, many surgeons employ an implantable device that can adjust, align and maintain the spatial relationship(s) between adjacent bones. An extensive array of surgical techniques and implantable devices have been formulated to accomplish this goal.
Symptomatic degeneration of the lumbar spine occurs most commonly at the L4/5 and L5/S1 levels and fusion of one or both of these segments has emerged as a common surgical procedure. Currently, these vertebral bodies may be fused using an anterior, lateral or posterior approach and each has particular advantages and draw backs. Frequently, circumferential fusion of the unstable level with fixation of both the anterior and posterior aspect of the spine is desired. This requires that patients undergo a combination of the aforementioned approaches. The anterior or lateral approaches are used to insert the bone graft into the disc space between the adjacent vertebras while the posterior approach is used to place bone screws or similar fasteners that are used to immobilize the vertebral bodies.
Access to the disc space for bone graft placement requires dissection through the vital tissues that lie anterior or lateral to the spine. U.S. Pat. No. 7,309,338 and others disclose a method for the access of the anterior column of the lumbar spine using a pre-sacral approach. (U.S. Pat. No. 7,309,338 is hereby incorporated by reference in its entirety.) The procedure has been popularized by the corporation TranS1, Inc of Wilmington, N.C. as the “AXLIF” procedure. The technology for both the L5 to S1 fusion procedure and the L4 to S1 fusion procedure are described on the web site “www.trans1.com”. All contents and disclosures of the web site are hereby incorporated by reference in their entirety. The procedure is further described in the article: A novel minimally invasive pre-sacral approach and instrumentation technique for anterior L5/S1 intervertebral discectomy and fusion. By Marotta et al., Neurosurg. Focus 20 (1): E9, 2006. The article is hereby incorporated by reference in its entirety.
With experience, an important shortcoming of the “AXLIF” procedure has been discovered. The procedure, which entails placement of a threaded screw or a threaded rod through an anterior segment of the sacrum and into the superior vertebral bones, fails to provide adequate segmental fixation in rotation and other planes of spinal motion. Thus, the “AXLIF” procedure must be supplemented with additional screw and orthopedic device stabilization in order to adequately immobilize the operative segment. Most commonly, posterior screw/rod fixation into the pedicle portion of the vertebral bones is used to supplement the “AXLIF” procedure. Unfortunately, the need to provide supplement fixation through alternative surgical corridors, such as the posterior approach to the spine, greatly limits the usefulness of the “AXLIF” procedure and obviates the advantages that the procedure provides over other current art.